Just use a bank with a decent service (like Revolut), create a separate card number for your kid (10s within the bank app), where you put more money when needed and can easily put the number on hold or activate it whenever you please.
https://cybernews.com/security/revolut-data-breach-75-millio...
> "We have checked the user and card identifiers contained in the alleged records against our systems, and none of them correspond to valid or genuine Revolut identifiers," the spokesperson said.
For sure, this feature is not a Revolut-exclusive. Plata from Mexico should also have this and much more, from what I have read.
If American/European banks don't have such a simple feature, this speaks volumes about them.
Your comment has a vibe of "a bank that doesn't have a local office has no decent service". To each their own, I guess.
if you're not in the US. revolut in the US is a fintech group with a bunch of bank partners.